Random artifacts/glitches on the screen - cause/fix? *Pics inside*

Discussion in 'iMac' started by HXGuy, Sep 15, 2010.

  1. HXGuy macrumors 68000

    Mar 25, 2010
    I've had my 27" iMac (3.06GHz) for a few weeks now and yesterday I noticed some weird artifacts appearing on the screen, very randomly.

    They will pop up all over the screen but if I "Show desktop", they will go away for a bit but sometimes reappear again in different areas of the screen. I restarted the computer but that only temporarily fixed the problem.

    Anyone know what's causing this and how to fix it?


  2. Hellhammer Moderator


    Staff Member

    Dec 10, 2008
    Try creating another user and see if it persists.
  3. Panch0 macrumors 6502a

    Feb 23, 2010
    Video Card

    As was suggested, see if it persists with a new user profile, but it's probably your video card. A new user profile should take any preferences you have changed out of the equation. You might also try stopping applications or removing them from your login items.

    My 4 year old iMac started doing this a couple of years ago. For the longest time, I thought it was an application issue, but eventually it degraded to the point that the screen would 'lock-up' after a few minutes use. Of course It didn't get to this point until my Apple Care was expired... Turns out that the video card is soldered to the motherboard and the fix is to replace the main logic board @ $550. Make sure you get this resolved while your warranty is still in effect, as it's a very costly repair.

    When this started happening on my system, It was from running the CPU hard for extended periods: Ripping DVDs in Handbrake and running games would reliably generate artifacts that would persist even after the system cooled back down.
  4. HXGuy thread starter macrumors 68000

    Mar 25, 2010
    Now that I think about it, after you mentioned that it would happen after running the computer hard, I think it is appearing after running Photoshop CS5 and/or QuarkXPress. I need to reset the computer, use it without those programs, see if it happens and if it doesn't, then open then up and see if it happens then.

    I bought the computer refurbished from Apple.com...do I have to go through Apple.com or can I go into a retail store for repair?
  5. HXGuy thread starter macrumors 68000

    Mar 25, 2010
    Just rebooted and so far so good, no artifacts.

    I have Mail, Calendar, Contacts, and 3 windows of Google Chrome open.
  6. HXGuy thread starter macrumors 68000

    Mar 25, 2010
    It just happened again when I opened iPhoto and looked at some pics. Closing iPhoto makes it go away but reopening makes the problem reappear.
  7. Thermonuclear macrumors 6502

    May 23, 2009
    I'd say that it is a problem with the GPU that's exacerbated by heating. I have a 2002 iMac G4 with the same issue. Also possible is that one or more of the cooling fans are failing.

    I'll guess that the problem will only get worse over time.

    The best solution would be to have the GPU replaced and I think an Apple tech can do this without replacing the entire system board. An alternative is to install some fan control software and have it run the fans faster or at lower temperature thresholds.
  8. HXGuy thread starter macrumors 68000

    Mar 25, 2010
    I wonder what triggered this...I guess something have have failed? I didnt do this for the first 3 weeks of ownership and now happens everytime I have too many things open. I just had 6 (8 page each) PDF documents open and sure enough it did it again. As soon as I closed 3 of the 6, the problem went away.
  9. Teqnilogik macrumors member

    Sep 16, 2010
    Could be video memory corruption or an issue with the GPU. Also consider your main RAM as a culprit as well. See if there is some RAM test you can run on it to rule out your main RAM as the problem. I'd call Apple to see about getting it repaired.
  10. HXGuy thread starter macrumors 68000

    Mar 25, 2010
    I went to the Genius Bar today and they said it looks like a video card problem and are replacing it. I'm dropping it of tomorrow. Hopefully it is the vid card and not the main RAM.
  11. HXGuy thread starter macrumors 68000

    Mar 25, 2010
    Did a search on Google for Mac RAM tests and found Rember which I ran and it said the system passed all RAM tests successfully.

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